The veteran manager has found it difficult to translate domestic supremacy into European success over the years, although United were crowned kings of Europe in 1999 and 2008.

FERGUSON THE FORMIDABLE

EUROPEAN RECORD AS MAN UTD BOSS

GAMES MANAGEDWINSDRAWSLOSSESTROPHIES WON

22412159444

And McQueen, who is recovering from throat cancer, insists that a Premier League and Champions League double would even supplant the 1999 treble season as the Scot's greatest accomplishment.

"You cannot ignore the challenge that faced United when rivals Manchester City won the league last season," he told Goal.com.

"It was a huge shock to everyone at United but they have responded magnificently well. There is no doubt that the signing of Robin van Persie has made all the difference.

"His goals have grabbed the headlines and taken some of the pressure of Wayne Rooney, who has thrived playing alongside the Dutchman.

"Sir Alex chose to play both of them against Everton just three days before the game in Madrid because he knew a 12-point lead in the league would give them breathing space to concentrate more on the Champions League.

"You will get a big debate among United fans over what is the more important – winning the league or the Champions League – but there is no doubt in my mind that Sir Alex's priority is the Champions League.

"He often talks about how they have underachieved in the Champions League and he is right because they should have won it at least four times under him.

"If they win the league and the FA Cup then it has been a good season but a league and Champions League double is something else. If they do that it will be an unmatched achievement because the standards in England and from sides like Madrid and Barcelona in Europe are far higher than they were in 1999."